Ideas from 'On the Plurality of Worlds' by David Lewis [1986], by Theme Structure

[found in 'On the Plurality of Worlds' by Lewis,David [Blackwell 2001,0-631-22426-2]].

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1. Philosophy / D. Nature of Philosophy / 4. Aims of Philosophy / a. Philosophy as worldly
Honesty requires philosophical theories we can commit to with our ordinary commonsense
1. Philosophy / F. Analytic Philosophy / 1. Analysis
Analysis reduces primitives and makes understanding explicit (without adding new knowledge)
3. Truth / A. Truth Problems / 6. Verisimilitude
Verisimilitude might be explained as being close to the possible world where the truth is exact
5. Theory of Logic / G. Quantification / 6. Plural Quantification
Quantification sometimes commits to 'sets', but sometimes just to pluralities (or 'classes')
7. Existence / A. Nature of Existence / 2. Types of Existence
There are only two kinds: sets, and possibilia (actual and possible particulars)
7. Existence / C. Structure of Existence / 5. Supervenience / a. Nature of supervenience
Supervenience concerns whether things could differ, so it is a modal notion
7. Existence / D. Theories of Reality / 6. Fictionalism
Abstractions may well be verbal fictions, in which we ignore some features of an object
7. Existence / D. Theories of Reality / 9. Vagueness / c. Vagueness as semantic
Vagueness is semantic indecision: we haven't settled quite what our words are meant to express
Whether or not France is hexagonal depends on your standards of precision
8. Modes of Existence / B. Properties / 1. Nature of Properties
Surely 'slept in by Washington' is a property of some bed?
Properties don't have degree; they are determinate, and things have varying relations to them
The 'abundant' properties are just any bizarre property you fancy
8. Modes of Existence / B. Properties / 2. Need for Properties
To be a 'property' is to suit a theoretical role
8. Modes of Existence / B. Properties / 4. Intrinsic Properties
A disjunctive property can be unnatural, but intrinsic if its disjuncts are intrinsic
All of the natural properties are included among the intrinsic properties
Global intrinsic may make necessarily coextensive properties both intrinsic or both extrinsic
If a global intrinsic never varies between possible duplicates, all necessary properties are intrinsic
8. Modes of Existence / B. Properties / 5. Natural Properties
We might try defining the natural properties by a short list of them
Natural properties give similarity, joint carving, intrinsicness, specificity, homogeneity...
We can't define natural properties by resemblance, if they are used to explain resemblance
Defining natural properties by means of laws of nature is potentially circular
I don't take 'natural' properties to be fixed by the nature of one possible world
Sparse properties rest either on universals, or on tropes, or on primitive naturalness
8. Modes of Existence / B. Properties / 10. Properties as Predicates
There is the property of belonging to a set, so abundant properties are as numerous as the sets
8. Modes of Existence / B. Properties / 11. Properties as Sets
A property is the set of its actual and possible instances
The property of being F is identical with the set of objects, in all possible worlds, which are F
If a property is relative, such as being a father or son, then set membership seems relative too
Trilateral and triangular seem to be coextensive sets in all possible worlds
I believe in properties, which are sets of possible individuals
It would be easiest to take a property as the set of its instances
Accidentally coextensive properties come apart when we include their possible instances
Properties don't seem to be sets, because different properties can have the same set
8. Modes of Existence / B. Properties / 13. Tropes / a. Nature of tropes
You must accept primitive similarity to like tropes, but tropes give a good account of it
8. Modes of Existence / B. Properties / 13. Tropes / b. Critique of tropes
Tropes need a similarity primitive, so they cannot be used to explain similarity
Trope theory (unlike universals) needs a primitive notion of being duplicates
Trope theory needs a primitive notion for what unites some tropes
8. Modes of Existence / D. Universals / 1. Universals
Universals recur, are multiply located, wholly present, make things overlap, and are held in common
If particles were just made of universals, similar particles would be the same particle
8. Modes of Existence / D. Universals / 3. Instantiated Universals
Universals aren't parts of things, because that relationship is transitive, and universals need not be
9. Objects / C. Structure of Objects / 8. Parts of Objects / c. Wholes from parts
Mereological composition is unrestricted: any class of things has a mereological sum
There are no restrictions on composition, because they would be vague, and composition can't be vague
9. Objects / D. Essence of Objects / 7. Essence and Necessity / a. Essence as necessary properties
An essential property is one possessed by all counterparts
9. Objects / E. Objects over Time / 1. Objects over Time
A thing 'perdures' if it has separate temporal parts, and 'endures' if it is wholly present at different times
9. Objects / E. Objects over Time / 2. Objects that Change
Properties cannot be relations to times, if there are temporary properties which are intrinsic
9. Objects / E. Objects over Time / 3. Three-Dimensionalism
Endurance is the wrong account, because things change intrinsic properties like shape
There are three responses to the problem that intrinsic shapes do not endure
9. Objects / E. Objects over Time / 12. Origin as Essential
I can ask questions which create a context in which origin ceases to be essential
9. Objects / F. Identity among Objects / 5. Self-Identity
Identity is simple - absolutely everything is self-identical, and nothing is identical to another thing
9. Objects / F. Identity among Objects / 6. Identity between Objects
Two things can never be identical, so there is no problem
10. Modality / D. Knowledge of Modality / 4. Conceivable as Possible / b. Conceivable but impossible
The impossible can be imagined as long as it is a bit vague
10. Modality / E. Possible worlds / 1. Possible Worlds / a. Possible worlds
There are no free-floating possibilia; they have mates in a world, giving them extrinsic properties
10. Modality / E. Possible worlds / 1. Possible Worlds / b. Impossible worlds
Possible worlds can contain contradictions if such worlds are seen as fictions
On mountains or in worlds, reporting contradictions is contradictory, so no such truths can be reported
10. Modality / E. Possible worlds / 1. Possible Worlds / c. Possible worlds realism
For Lewis there is no real possibility, since all possibilities are actual
Lewis posits possible worlds just as Quine says that physics needs numbers and sets
For me, all worlds are equal, with each being actual relative to itself
If possible worlds really exist, then they are part of actuality
A world is a maximal mereological sum of spatiotemporally interrelated things
10. Modality / E. Possible worlds / 1. Possible Worlds / d. Possible worlds actualism
Lewis rejects actualism because he identifies properties with sets
Ersatzers say we have one world, and abstract representations of how it might have been
10. Modality / E. Possible worlds / 2. Nature of Possible Worlds / a. Nature of possible worlds
Ersatz worlds represent either through language, or by models, or magically
10. Modality / E. Possible worlds / 2. Nature of Possible Worlds / b. Worlds as fictions
Linguistic possible worlds need a complete supply of unique names for each thing
Maximal consistency for a world seems a modal distinction, concerning what could be true together
Linguistic possible worlds have problems of inconsistencies, no indiscernibles, and vocabulary
10. Modality / E. Possible worlds / 2. Nature of Possible Worlds / c. Worlds as propositions
If sets exist, then defining worlds as proposition sets implies an odd distinction between existing and actual
10. Modality / E. Possible worlds / 3. Transworld Objects / c. Counterparts
A counterpart in a possible world is sufficiently similar, and more similar than anything else
In counterpart theory 'Humphrey' doesn't name one being, but a mereological sum of many beings
The counterpart relation is sortal-relative, so objects need not be a certain way
Why should statements about what my 'counterpart' could have done interest me?
10. Modality / E. Possible worlds / 3. Transworld Objects / d. Haecceitism
Extreme haecceitists could say I might have been a poached egg, but it is too remote to consider
Haecceitism implies de re differences but qualitative identity
Extreme haecceitism says you might possibly be a poached egg
13. Knowledge Criteria / C. External Justification / 2. Causal Justification
General causal theories of knowledge are refuted by mathematics
14. Science / C. Induction / 2. Aims of Induction
Induction is just reasonable methods of inferring the unobserved from the observed
14. Science / C. Induction / 5. Paradoxes of Induction / a. Grue problem
To just expect unexamined emeralds to be grue would be totally unreasonable
14. Science / D. Explanation / 2. Types of Explanation / f. Causal explanations
An explanation tells us how an event was caused
Often explanaton seeks fundamental laws, rather than causal histories
14. Science / D. Explanation / 2. Types of Explanation / k. Probabilistic explanations
If the well-ordering of a pack of cards was by shuffling, the explanation would make it more surprising
18. Thought / D. Concepts / 6. Abstract Concepts / a. Abstract concepts
Abstraction is usually explained either by example, or conflation, or abstraction, or negatively
18. Thought / D. Concepts / 6. Abstract Concepts / c. Abstracta by ignoring
The Way of Abstraction says an incomplete description of a concrete entity is the complete abstraction
18. Thought / D. Concepts / 6. Abstract Concepts / d. Abstracta by example
The Way of Example compares donkeys and numbers, but what is the difference, and what are numbers?
18. Thought / D. Concepts / 6. Abstract Concepts / f. Abstracta by conflation
If we can abstract the extrinsic relations and features of objects, abstraction isn't universals or tropes
Abstracta can be causal: sets can be causes or effects; there can be universal effects; events may be sets
If abstractions are non-spatial, then both sets and universals seem to have locations
If universals or tropes are parts of things, then abstraction picks out those parts
18. Thought / D. Concepts / 6. Abstract Concepts / g. Abstracta by equivalence
For most sets, the concept of equivalence is too artificial to explain abstraction
The abstract direction of a line is the equivalence class of it and all lines parallel to it
18. Thought / D. Concepts / 6. Abstract Concepts / h. Abstractionism critique
We can't account for an abstraction as 'from' something if the something doesn't exist
19. Language / B. Meaning / 7. Meaning by Role
A particular functional role is what gives content to a thought
19. Language / E. Propositions / 2. Nature of Propositions
A proposition is the property of being a possible world where it holds true
A proposition is a set of entire possible worlds which instantiate a particular property
Propositions can't have syntactic structure if they are just sets of worlds
26. Natural Theory / B. Concepts of Nature / 4. Time / h. Growing block of time
It is quite implausible that the future is unreal, as that would terminate everything
26. Natural Theory / C. Causation / 3. General Causation / c. Counterfactual causation
Causation is when at the closest world without the cause, there is no effect either